First record of three African trichodinids (Ciliophora: Peritrichida) in cultured Nile tilapia (Oreochromis niloticus) in Saudi Arabia with re-evaluation of their host specificity

Saudi Arabia has a developing aquaculture industry that farms primarily tilapia. Although trichodinids are presumably the most usually encountered protozoan parasites in these cultured fish, they have rarely been studied in this context, and there is no data on the species that might infect cultured tilapia in Saudi Arabia. The present study was therefore carried out as a general survey to investigate the occurrence and identify the species of trichodinids that can infect cultured tilapia (Oreochromis niloticus) in Saudi Arabia. A total of 500 tilapia fish were collected from fish farms in Riyadh city and examined in order to determine the species of trichodinids present in the positive specimens. Three species of trichodinids (Trichodina maritinkae, T. centrostrigeata and T. frenata) were isolated and described as new records in Saudi Arabia. These trichodinids were found simultaneously in the same fish with overall prevalence of 20% (100/500). The identification and characterization of these three species are documented based on Riyadh specimens, for the first time. Additionally, the present paper confirms the existence of T. frenata for the second time globally and establishes this trichodinid as a new parasite for O. niloticus. T. maritinkae is highly specific to clariids, and previously, it has not been reported from any fish species other than clariids. The present work also confirmed that T. centrostrigeata can also infest cichlid fish. The list of host records of these species is expanded and their host specificity re-evaluated based on the results of this study in addition to the previously published data. We conclude that there is a need for further study of the impacts of these Trichodina spp. on Saudi Arabian fishery sector.

Isospora riyadhensis n. sp. (Apicomplexa: Eimeriidae) from the worm lizard Diplometopon zarudnyi Nikolskii (Amphisbaenia: Trogonophidae) in Saudi Arabia

Isospora riyadhensis n. sp. is described from the intestine of the worm lizard Diplometopon zarudnyi Nikolskii in Saudi Arabia, where its prevalence was 26.6%. Its oöcysts are spherical to subspherical and measure 23 × 20 μm. The sporocysts, which are tetrazoic and ovoid, measure 13 × 8 μm, whereas their sporozoites are banana-shaped, have anterior and posterior refractile bodies and measure 12 × 3 μm. Oöcysts are passed unsporulated, and the majority become fully sporulated within 3 days at 25 ° C. All endogenous stages develop in the cytoplasm of epithelial cells in the posterior region of the small intestine, from where meronts, microgamonts and macrogamonts are described.

Auerbachia bajadi sp. n. (Myxozoa: Auerbachiidae) infecting the gallbladder of orangespotted trevally Carangoides bajad (Teleostei: Carangidae) in the Red Sea

Light microscopic description was presented for a new myxosporean species, Auerbachia bajadi. The parasite was collected from the gallbladder of orangespotted trevally Carangoides bajad (Forsskål, 1775) in Al-Quseir city, Red Sea coast, Egypt. The prevalence was 30/80 (37%) and the infection was reported as an enormous amount of free mature spores floating in the bile. Spores were club-shaped with a broad anterior part and a narrow caudal part. Shell valves were asymmetrical and the larger valve was drawn into a wide caudal projection. The mean spore measurements were 22.7 mum in total length and 9.5 mum in width. Polar capsule was single and elliptical-shaped with five polar filament turns. The polar capsule measured 9.5 mum in length and 4.5 mum in width. The spores were distinctly different from the four recorded species of genus Auerbachia. One of the cited species of this genus was excluded as it was related to genus Coccomyxa than genus Auerbachia. Also, the accurate citation date of this genus was discussed.

Light and electron microscopic study on Henneguya suprabranchiae Landsberg, 1987 (Myxozoa: Myxosporea) infecting Oreochromis niloticus, a new host record

Out of 58 live tilapia fish, five Oreochromis niloticus were found to be naturally infected with Henneguya suprabranchiae (8.62%). Such infection was recorded only during winter season from Bahr Shebin, a tributary of the River Nile at Menoufia Governorate, Nile Delta, Egypt. Based on the structure and measurements of fresh spores, this parasite was identified as H. suprabranchiae. Spores are oval in shape and they measure 15 (13-16) x 5 (4-6) microm length by width. It has two polar capsules inside and they measure 4 (5-7) x 1 (2-3) microm length by width. Each polar capsule has spirally coiled (7-9 turns) polar filament. The plasmodia as well as all other parasitic stages were described using light and transmission electron microscopy and discussed regarding to those of other fish hosts especially those of Africa.